Hadith 1:656

Narrated Aisha:

the mother of the believers: Allah's Apostle during his illness prayed
at his house while sitting whereas some people prayed behind him
standing. The Prophet beckoned them to sit down. On completion of the
prayer, he said, 'The Imam is to be followed: bow when he bows, raise
up your heads (stand erect) when he raises his head and when he says,
'Sami a-l-lahu liman-hamida ' (Allah heard those who sent praises to
Him) say then 'Rabbana wa laka-l-hamd' (O our Lord! All the praises
are for You), and if he prays sitting then pray sitting."